OT: remote control central locking etc

[Grumps]

This is really OT. I have a 206 van (2001) with remote control central locking. The range of the transmitter seemed to be quite good, at least 15m. Then, one day, I noticed that the range was very short at home, but still ok when I get to work. I didn't really think anything of it. Now I have another car (BMW 530d, 1999) which seems to have the same problem; low range at home (i.e. the key needs to be right by the car's window for it to work) but ok elsewhere (except Carrefour in Cherbourg!). And I have another car (BMW 525tds 1993) which has a decent range everywhere. So the question is what can cause this apparent localised interference to 'modern' systems, but not my older car? Are there known interference problems of this type? I did switch off the mains to my house suspecting that there was something here that could cause a problem, but it's not me. I'm going to plot the range at various places araound where I live. This is beginning to bug me now.

[Matt Beard]

I think that the modern remote central locking devices use the same band as digital cordless phones and wireless home networking. This changed some time in the last ten years.

If my befuddled memory is right that would, perhaps, explain things.

[getbent]

I used to have a weird problem. Whenever I parked outside Bickley train station, near Bromley, my remote central locking wouldn't work, on a 2000 Vectra. The first time I found it wasn't working, I drove to the local Vauxhall dealer, where I promptly found that it was working again.

Doesn't help you in any way, but at least you're not alone!

[Grumps]

So every time I stand outside relentlessly trying to get my car unlocked, someone, somewhere, has a home network having errors? That gives me some satisfaction (although the RF level of my remote is probably far less power than those wireless networks). It could even be my own cordless phone!

[dennis]

Wireless alarms, my outside thermometer, other stuff operate on the same frequency as my car remote (IIRC ~432MHz). No where near cordless phones or wireless LANs.

But any powerful transmitter could interfere with the low cost receivers used in cars. Hence the cars that wont open at airports.

[Tim Mitchell]

In article , Matt Beard writes

It's true that the frequencies used by remote locking transmitters are unlicensed and shared by many different types of product, however DECT phones and wireless networks are not among them.

The freqs are usually 433MHz or 868MHz. Dect is on 1.8GHz and wifi is

2.4GHz.

It could be that if there is a wifi or DECT base station in a nearby house, the receiver of the car is being saturated by it and can't "hear" the signal on the other frequency. This can also happen with cellphone base station masts.

[manatbandq]

Search for "tetra central locking site:uk" in Google

MBQ

[Mike Harrison]

It is not likely to be another device on the 433 band, as these have limited duty-cycles, i.e. only transmitting occasionally (unless faulty, or, say, a keyfob at the bottom of a drawer with stuff piled on it holding the button down, although the battery would die pretty quickly) It is far more likely to be an out-of-band signal that either has a harmonic in the receiver's range, or is just overloading it. If it happens all the time then that limits the probably cause to something that is always on - a nearby cellphone basestation, wireless network or video sender would probably be the most likely candidates, although interference from an unintentional radiating item that just happens to be at an unfortunate frequency could also cause problems.

[Spike]

Mobile phone masts can cause this. Got one near you?

[Michael Chare]

I have found that I can increase the range of my VW central locking remote control by holding the metal keyring end to my head.

I don't know what this does to my brain!

(A point I learnt from the BBC2 Sunday evening motoring programme.)

[Grumps]

Cherbourg!).

No.

[Grumps]

Yes, that normally works. But not in this case.

[mike ring]

I'm an absolute anti petrol-head, but I like the prog; it seems the last place in this doomridden country where anybody is allowed to have fun.

The method increases the rather short range on my m/cycle alarm by many times.

I've found out that handy railings, traffic signs, stink-pipes, etc also work well if you have an brains left to worry about

mike

[Grumps]

Cherbourg!).

Hmm. Sounds like it could be this. So, I'm stuffed then!?

[<me9]

They often use simple receivers and are around 450MHz, which is populated by many other users. I notice mine has poor range generally in car parks, and particularly in the town hall car park, which is adjacent to the police station and it's communications facilities.

[Matt Beard]

Yes, it seems that my befuddled memory had it the wrong way! They were all moved into the 433Mhz band. This is frequency surrounded by lots of military stuff!!

[Matt]

There were originally two UK "unlicenced" low power allocations in the

400-500Mhz range. I can't recall exactly what the other was (418MHz?) but only one of the two is now permitted for short duration signals such as the remotes use.

The other was allocated but only for so many years but its now being reallocated and used by something else (TETRA PMR I think) hence the intermittent problems with car remote usage - this might be the 433MHz or it might be 418MHz.

[Dave]

Not much military stuff at that frequency, but lots of radio amateurs. They use simplex and split frequency working. 433 MHz being the centre of activity.

I have 2 Rover 45's and last night I could not lock or un-lock either of them, but I do have a radio ham across the road and I know he uses this frequency. Half an hour later, they both worked perfectly.

HTH

Dave

[Huge]

Ah. 433MHz, aka 70cms.

[Dave]

Yup, one and the same.

Dave

A radio ham for over 30 years, but I have never stopped myself from locking/un-locking my car.